Hi All, Are multi-channel (more than 2) formats fully supported in the OggVorbis specification ? I couldn't find any information about multi-channel support on xiph.org. I've used 'oggdropXPd' to encode a 5.1 wavefile and the Xiph OggVorbis libraries (vorbisfile.dll) to decode the file successfully, however the order of the channel interleaving is different to the original wave file (a 5.1 WAVEFORMATEXTENSIBLE file). Is the channel order specified for OggVorbis files, or is there a way I can retrieve this information from the file itself ? On a related note ... do any of the encoders assume that a particular channel contains LFE only ? Thanks for any help you can give me. Dan -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.xiph.org/pipermail/vorbis/attachments/20060626/badfff1d/attachment.html
Section 4.3.9 Output Channel Order of the Vorbis I Spec refers. If you use oggdropXPd to decode the file, the output channels will be remapped from the vorbis channel map onto the requiements of WAVEFORMATEXTENSIBLE and will contain the correct header. John Daniel PEACOCK wrote:> Hi All, > > Are multi-channel (more than 2) formats fully supported in the OggVorbis > specification ? I couldn't find any information about multi-channel > support on xiph.org. I've used 'oggdropXPd' to encode a 5.1 wavefile and > the Xiph OggVorbis libraries (vorbisfile.dll) to decode the file > successfully, however the order of the channel interleaving is different > to the original wave file (a 5.1 WAVEFORMATEXTENSIBLE file). Is the > channel order specified for OggVorbis files, or is there a way I can > retrieve this information from the file itself ? > > On a related note ... do any of the encoders assume that a particular > channel contains LFE only ? > > Thanks for any help you can give me. > > Dan > > > ------------------------------------------------------------------------ > > _______________________________________________ > Vorbis mailing list > Vorbis@xiph.org > http://lists.xiph.org/mailman/listinfo/vorbis > > > ------------------------------------------------------------------------ > > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.1.394 / Virus Database: 268.9.4/375 - Release Date: 25/06/2006
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On Mon, Jun 26, 2006 at 02:12:15PM -0700, Daniel PEACOCK wrote:> Are multi-channel (more than 2) formats fully supported in the OggVorbis specification ? I couldn't > find any information about multi-channel support on xiph.org. I've used 'oggdropXPd' to encode a > 5.1 wavefile and the Xiph OggVorbis libraries (vorbisfile.dll) to decode the file successfully, > however the order of the channel interleaving is different to the original wave file (a 5.1 > WAVEFORMATEXTENSIBLE file). Is the channel order specified for OggVorbis files, or is there a way > I can retrieve this information from the file itself ?Multi-channel audio is fully supported in the Vorbis format, however there are a number of bugs with current encoders and decoders with respect to channel order. That's probably what you're seeing. We're working to get those fixed this summer; I believe recent releases of illi's DirectShow and Arek's Quicktime components do the correct thing, as well as latest gstreamer. The commandline oggenc is still ignoring the WAVEFORMATEXTENSIBLE channel mapping table. The spec does specify a fixed channel order for streams with one to six channels (and six is 5.1 surround in the dolby configuration). See section 4.3.9 "output channel order". Unfortunately there is no way to distinguish within the stream itself between various surround configurations and generic multitrack audio which happen to have the same number of channels. The "Ogg Skeleton" enhanced metadata proposal is probably the best place to do so if you need this. For normal surround playback just getting everyone using the prescribed order is sufficient.> On a related note ... do any of the encoders assume that a particular channel contains LFE only ?All the the encoders I know treat multichannel (>2) audio as a set of independent streams which is of course not very efficient. There is some low hanging fruit here in adding channel coupling and an implicit low-pass on the LFE channel for 5.1 surround. As far as doing a properly tuned mode, Monty has said that his ignorance of 5.1 mixing techniques (and the lack of lossless masters to listen/experiment with) has kept him from doing much. However, both he and aoyoume-san are interested in working on surround modes. This is something where we really need the help of larger organizations and artists working in surround. Hope that answers your question, -r
On 26 Jun 2006 at 23:13, John Edwards wrote:> Section 4.3.9 Output Channel Order of the Vorbis I Spec refers. > > If you use oggdropXPd to decode the file, the output channels will be > remapped from the vorbis channel map onto the requiements of > WAVEFORMATEXTENSIBLE and will contain the correct header.While we're at it: Is there a utility (for MS-Windows) to encode directly from an SPDIF input? Considering the temporary memory required for a 5.1/24bit stream (maybe 96kHz) direct encoding seems useful. Also, a short 5.1 Vorbis sample would be good. Regards, Ulrich
On 26 Jun 2006 at 15:20, Ralph Giles wrote: [...]> low-pass on the LFE channel for 5.1 surround. As far as doing a properly > tuned mode, Monty has said that his ignorance of 5.1 mixing techniques > (and the lack of lossless masters to listen/experiment with) has kept > him from doing much. However, both he and aoyoume-san are interested inIf you consider "lossless" as no more loss than what comes out of a DVD digitally, the problem is not the lack of having such a sample, but to have one with a permitting license ;-) Ulrich